Several methods for teaching serial position sequences to monkeys

Three keys were available for monkeys to press. The objective was to teach the animals to press the keys in sequences up to 10 members in length. With fading procedures, a light that cued the correct key at a given serial member of the sequence faded out slightly each time the animal selected it, and became slightly brighter after the animal made an error at that sequence member. The correct keys were faded out, starting from the end of the sequence and proceeding toward the beginning. With control procedures, the cue lights were turned off suddenly, rather than being faded gradually. In almost every instance, the animals learned a longer series of unlighted key positions with the fading procedures than they did when each key-light was turned off suddenly. Also, requiring the animals to press a series of keys cued by lights before they could reach the sequence members they were to learn hampered them in learning the later serial members. By using several different sequences, it was possible to replicate these findings within the individual animal.     

Delayed discrimination and delayed matching in pigeons

Three pigeons were each trained to perform a discrimination problem and a matching problem. Following acquisition, delays of 1 to 7 sec were interposed after stimulus presentation on both problems. Accuracy of responding on these two types of delay procedures was observed to be a function of length of delay interval. Performance was consistently poorer on the delayed matching problem than on the delayed discrimination problem.     

The psychological refractory period as a function of performance of a first response

Proponents of a “single channel” theory of the psychological refractory period have not specified whether the single channel occupies only the decision component of the response selection, only the motor or response component, or both. In this experiment, the delay in the RT to the second of two successively presented stimuli was examined as a function of whether or not an overt motor response was made to the first stimulus, keeping the decision component constant. It was found that in both conditions RT₂ was delayed, suggesting that the decision component was a part of the single channel. However, RT₂ was delayed by a significantly greater amount if a motor response was required, indicating that the motor component is part of the single channel as well. Implications of the results for an expectancy theory of the psychological refractory period are discussed.     

Contralateral and heteromodal interaction effects in somatosensation: Do they exist?

In this paper we concern ourselves with the problem of whether or not conditioning stimuli of other modalities or stimuli applied to a distant locus of the body interact with a sensitive test of somesthetic temporal acuity we have called the gap test. The results of the experiment indicate that visual stimuli do not exert an observable influence on this temporal judgment, but that auditory stimuli and contralateral stimulation in the same modality do show a significant but relatively small effect. This is compared and contrasted with the very large and persistent effect reported when the conditioning stimulus is applied to the same electrodes as the gap test. By comparing our results with experiments of similar design carried out on lower animals by other investigators, some insights into the neural localization of the reported effects is obtained.     

The true distributions of the range of rank totals in the two-way classification

This paper presents the results from an investigation of the true probability distributions of the range of rank totals. A procedure for generating an approximation to the true distributions is also given. A comparison of the results of this approximation with an extensive criterion of generated true and sample distributions, and with other approximations is indicated. Accurate estimates of the critical ranges necessary to reach significance at three commonly used alpha levels, where the number of judges and items is less than or equal to sixteen, are presented in tabular form.